An engine/generator combination is generically referred to as a generator set. One specific application for a generator set is to supplement the main power service for a facility. When using a generator set in this manner, it is necessary to start the engine, then synchronize the generator output to the phase, order, zero crossing and voltage of the power on the power bus to which the generator is connected. Used in this manner the generator set can supplement the power on the power bus during periods of peak demand from the manufacturing plant or facility. In order to synchronize the generator output with the power bus, a synchroscope is generally connected between the different phases of the power bus and the different corresponding phases of the generator output to display the phase difference between the two power supplies. Based on the synchroscope output, the operator can adjust the engine speed to modify the phase of the generator set output in an attempt to match the output phase of the generator with the phase of the power bus. When the two phases are within a predetermined tolerance of one another, and the voltages, order and zero crossings are all within their respective tolerances, the operator can connect the generator set to the power bus.
Although the synchroscope generally performs satisfactorily there are disadvantages associated with its use. First, it must be manually connected to the power bus and to the generator output each time it is used or, if it is connected permanently, then the resulting extra hardware increases the cost of the system. It would be preferable to have a generator controller that included a synchroscope mode.